|• Wastes and energy crops|
Natural energy flows and sources such as sunlight, the winds, waves and tides offer a relatively clean, safe and above all sustainable source of power. This chapter explores the renewable energy options, looking at the basic technology and at some current developments, and then reviews the overall global resource potential of renewable energy.
Renewable energy technology
Renewable energy is so called because it relies on natural energy flows and sources in the environment which, since they are continuously replenished, will never run out. So they meet our first criterion for sustainability. In what follows, to provide a context, we first look at the basic technology before moving on in Chapter 7 to look at developments around the world.
The basic technology is very varied, reflecting the range of natural energy sources. As has been indicated, most sources of renewable energy are the result, directly or indirectly, of the impact of solar radiation on the planetary ecosystem—the exceptions being tidal energy flows and geothermal heat. Incoming solar radiation provides energy for plant and animal life and drives the hydrological weather cycle—evaporating sea water and creating rain which feeds into rivers and streams. Local differential heating of the atmosphere, sea and land also causes winds, which move over the seas creating waves. By contrast tidal energy could be thought of as lunar power, given that the main component is due to the